Twisting device for the SZ twisting of electrical cables

ABSTRACT

An improved twisting device for imparting a twist to the stranding elements of electrical cables, which twist alternates from section to section, in which two fixed twisting heads have installed between them a pair of movable twisting heads on a common frame which is moved back and forth thereby forming a pair of accumulators of alternatingly variable size as the movable twisting heads are moved back and forth.

United States Patent [191 Oestreich et al.

[ TWISTING DEVICE FOR THE SZ TWISTING OF ELECTRICAL CABLES [75] Inventors: Ulrich Oestreich, Berlin; Wolfgang Katzschner, Neustadt, Coburg, both of Germany [73] Assignee: Siemens Aktiengesellschaft, Munich,

Germany 22 Filed: June 21,1973

21 App1.No.:372,341

[30] Foreign Application Priority Data June 28, 1972 Germany 1. 2232329 [52] US. Cl 57/34 AT; 57/59 [51] Int. Cl. H0lb 13/04 [58] Field of Search 57/34 AT, 59, 60, 34 R, 57/156, 160

[56] References Cited UNITED STATES PATENTS 3,481,127 Vogelsberg 57/34 AT [4 1 May 20, 1975 3,491,525 l/l97O Sugi 57/34 AT 3,507,108 4/1970 Yoshimura et al.. 57/34 AT 3,645,079 2/1972 Stoebner 57/34 AT 3,782,092 1/1974 Vogelsberg 57/34 AT FOREIGN PATENTS OR APPLICATIONS 1,468,382 12/1966 France 57/34 AT Primary Examiner.lohn Petrakes Attorney, Agent, or F irm-l enyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT 6 Claims, 3 Drawing Figures PATENYED W20 SHEET 2 OF 2 TWISTING DEVICE FOR THE SZ TWISTING OF ELECTRICAL CABLES BACKGROUND OF THE INVENTION Various methods and devices have recently been developed for twisting electrical cables such as communication cables so that the cable elements forming a finished cable unit are alternately twisted with a left hand twist and a right hand twist. Left hand twists are generally referred to as S-twists and right hand twists as Z- twists. In general, the type of twisting wherein S and Z- twists alternate are called SZ twists. These devices which have recently been developed have the advantage that the elements to be twisted can be unwound from stationary supply frames and that further processing of the SZ twisted units can follow in a single operation.

Each of the devices used for performing such twisting generally uses revolving twisting devices and often include an accumulator wherein a twist of one direction or the other may be stored. In some, accumulators of a fixed content are used and revolve with a speed or direction of rotation which changes from section to section with the velocity of the cable through the unit remaining constant. Such a device is shown in US. Pat. No. 3,169,360. It is also possible to have accumulators of fixed content which revolve at a constant speed and direction of rotation and in which the velocity of the cable elements through the accumulator is changed from section to section. Such a system is shown in French Pat. No. 1,468,382. Some twisting devices of this nature also include an accumulator which has a content which may be increased or decreased. In such devices the content is alternatingly increased and decreased while the rotary motion of the accumulator remains constant. This is shown in German Pat. No. 1,665,831, U.S. Pat. No. 3,373,550, and in MTZ 1970, No. 9, pp. 472-80. Another type of twisting device uses a stationary accumulator around which flying, twisting yokes rotate. Such a device is shown in German Pat. No. 1,665,538.

Generally, the accumulators previously used for S-Z- twisting comprises two groups of rollers arranged on parallel axis. The stranding elements to be used in making the cable unit are led alternatingly around one roll of the one group of rollers and subsequently around a roll of the other group of rollers. Additionally, pulley like designs may be used in an accumulator as shown in German Offlengungschrift 1,817,803. Further, accumulators having two twisting heads which are arranged at a fixed distance from each other and are rigidly coupled to each other in regard to their rotary motions have been used, for example, see Wire & Wire Products, l/67, pp. 90-7 and 159-60. A practical embodiment of this which uses a caterpillar chain is shown in German Offlengungschrift 1,515,730.

In using accumulators of variable storage content, i.e., where one group of rollers is stationary and the other one movable back and forth in the direction of the twisting axis, it is advantageous to connect two such accumulators in tandem in a twisting stage. In such an arrangement the rates of change of the storage contents of the two accumulators are made opposite to each other and their relative angular velocities preferably adjusted such that the angular velocity of one accumulator with respect to the second accumulator is not equal to zero. Preferably both accumulators are revolved at the same speed but with opposite directions of rotation. An apparatus illustrating some of these principles is shown in US. Pat. No. 3,481,127 particularly in FIG. 2.

In SZ twisting methods in which the accumulators have groups of rollers and the stranding elements are sometimes led through the roller unsupported, parallel or nearly parallel to the axis of the rotation of the accumulator and at a distance from the axis which is up to about one half the diameter of the rollers. During the twisting, as the accumulator rotates, forces are exerted on the stranding elements which forces are proportional to the distance of the elements from the axis of rotation. This leads to high stressing of the stranding elements. Thus, the speed of rotation of the accumulator and thus the maximum speed at which the finished unit can be drawn off is often limited by the allowable tensile stresses which may be placed on the individual elements.

The above mentioned accumulator of German Offlengungschrift 1,515,730 comprises two rigidly coupled twisting heads which are arranged at a fixed distance from each other and between which the stranding elements are held in a stretched condition. This aids to some degree in the problems associated with the stresses on the stranding elements. Twisting heads which grip the stranding elements combined into a strand frictionally and hold them in a stretched condition to avoid such stresses are shown in the journal Draht volume 22 (1971) No. 9, page 619-625. However, this particular apparatus operates without using the types of accumulators described above. A type of twisting head which will grip the strand in this manner to hold it stretched is disclosed in German Pat. No. 1,765,452.

SUMMARY OF THE INVENTION The present invention provides an improved SZ twisting device which operates using accumulators which have a variable storage content otherwise referred to as breathing accumulators. To solve the above mentioned problems associated with the prior art accumulators, the present invention provides at least one revolving accumulator having a storage content which is increased and decreased at intervals and also includes means for drawing the wire off reels and means for winding up the completed stranded cable unit. The accumulator comprises a rotating first twisting head stationary in the direction of the twisting axis, and a second twisting head rotating in the same direction as the first stationary head but which is moved back and forth along the twisting axis with respect to the first twisting head. Each of the twisting heads grips the stranding elements, which are combined into a strand, frictionally in the direction of the circumference of the rollers in a twisting head which holds the strand in a stretched condition gripping in such a manner so that the pulling through of the strand is not materially affected.

In the practice of the present invention it is essential that the stranding elements which are combined into a strand are maintained in a stretched condition between two twisting points which are immediately ahead of and immediately behind the twisting heads in the accumulator. Because of the stretched disposition, essentially no centrifical forces are exerted on the stranding elements as they run through the accumulator. In addition, me-

chanical stresses caused by running over deflection rollers are also avoided. This results in the ability to have an increased speed of production, i.e. the speed of rotation of the twisting device along with the drawing off speed can be substantially increased. Speeds of up to 6,000 rpm and drawing off speeds of up to 200 meters per minute are possible.

The manner in which the stranding elements are stretched as they run through the accumulator, eliminating the use of deflection pulleys also makes it possible to make the distance between the twisting heads and the corresponding twisting points extremely short. This in turn makes it possible to substantially shorten the lengthwise section which develop at the reversal points of twist direction. (These points are not twisted or only twisted a small amount so they should be kept as small as possible). This in turn has a beneficial effect on the electrical coupling of the twisted units as they are later twisted with each other to form a final cable. In a preferred embodiment of the present invention two twisting stages are arranged in tandem, each having an accumulator of the type described above. The two accumulators revolve with opposite directions of rotation and change their storage contents in opposite senses. Preferably, in this embodiment having tandem accumulators, the second twisting head of the first accumulator and the first twisting head of the second accumulator are supported directly adjacent to each other in a frame which is movalbe back and forth in a lengthwise direction, i.e. in the direction in which the strand is running through the accumulators. This results in a simplified design of the twisting device.

As noted above, the twisting heads used must grip the stranding elements frictionally in the direction of the circumference of the rollers of the twisting heads in such a manner as to firmly hold the strand but to still allow it to be easily pulled through. To accomplish this a particularly advantageous twisting head which comprises essentially one or several pairs of rollers arranged on parallel axis and facing each other and in which the strand elements run between the running surfaces of the rollers and are frictionally gripped thereby is shown. In such an embodiment the elements are held between the two rollers which are pressed together and thus maintained in a stretched condition. The design of the rollers is such that the strands are firmly held but that the pulling through of the strand is not impeded. This is accomplished by forming the rollers so that there is a groove in the running surface running in the direction of the circumference and extending approximately over the entire width of the running surface. In particular, a friction lining of rubber-elastic material is embedded in such a manner that a hollow space remains between the elastic surface and the bottom of the groove of the roller in which it is inserted. Thus, the portion of the roller which grips the strands can flex down providing the needed groove to firmly grip the strands but still permit ease of pulling through. In the preferred embodiment this friction winding is made in a U-shaped cross section and with the ends of the legs of the U firmly connected to the roller and the bottom of the U forming the friction member which contacts the strands and forms the running surface of the roll.

In operating with the SZ twisting device of the present invention the two twisting heads of the accumulator will generally revolve with the same direction of rotation and the same rotational speed. The design of the accumulator is such that as the stranding elements run through the accumulator in a stretched condition only halfa turn is stored between the twisting heads as compared to the prior art accumulators having groups of rollers arranged on parallel axis. This makes it possible to let the twisting heads of an accumulator rotate simultaneously at different speeds of rotation. In this manner a modulation of the lay of the S2 twisted units is accomplished; that is, the length of lay of the S2 twisted units produced is not constant over the length of the unit but varies continually within definite limits. This has a beneficial effect on the electric decoupling of the SZ twisted units when they are later twisted together to form a complete twisted cable group. It is additionally possible to control the speed of rotation of one or all of the twisting heads according to a predetermined program, i.e. continuously or at intervals.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of the preferred embodiment of the twisting device of the present invention showing two tandem accumulators having twisting heads on a common movable frame.

FIG. 2 is an elevation view partially cut away illustrating the preferred type of twisting head for use in the present invention.

FIG. 3 is a plan view partially in cut away section of the twisting head of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An elevation view of the preferred embodiment of the present invention is illustrated by FIG. 1. Four wires 40 are taken from stationary wire supplies 4], such as reels, across pulleys 42 supported by a frame 43 to a laying top 56 where they are combined into a strand. The laying top 56 which forms a first twisting point is located in one end 62 of the frame of the twisting device designated generally as 50. The wires 40 which have been formed into a strand run through the twisting device 50 and are formed into a spiral quad 45 which then is fed over a deflection pulley 57, to a drawing pulley 58, around which the spiral quad 45 is looped once, to a takeup drum 60 supported by a frame 61. Drawing pulley 58 is supported by a frame 59. The twisting device 50 in general comprises four twisting heads 51, 52, 53 and 54. Twisting heads 51 and 52 form a first variable or breathing accumulator and twisting heads 53 and 54 a second similar accumulator. Twisting head 51, a stationary twisting head has as its twisting point the laying top 56. The twisting point for twisting head 54 is the deflection pulley 57. The twisting heads 52 and 53 have as their twisting points the other respective twisting heads, i.e. the twisting point for twisting head 52 is twisting head 53 and that for twisting head 53 is twisting head 52. Twisting head 51 is driven through belt 66 by a motor 65. Twisting head 54 is driven through a belt 71 by a motor 70. Similarly twisting heads 52 and 53 are driven respectively by motors 73 and 74 through belts 67 and 72.

Twisting heads 51 and 54 are supported for rotation respectively in the ends 62 and 63 of the machine frame. Twisting heads 52 and 53 are rotatively supported in the frame 75. Frame or housing 75 is supported by guide rods running between the ends 62 and 63 (not shown). Motors 73 and 74 are secured to the housing 75 on its underside. The twisting heads 51 through 54 are preferably driven so that they always revolve with a uniform speed and direction of rotation. The direction of rotation of twisting heads 51 and 52 is opposite to that of twisting heads 53 and 54. In order to alternately increase and decrease the storage content of the accumulators formed by the twisting heads, a threaded shaft 76 is provided which contains cross threads which engage threads in the extending arms 79 and 80 of the housing 75. A pulley is securely attached to the shaft 76 so that it may be driven by the motor 65. Alternatively, a separate motor may be provided for driving shaft 76. The cross threads on the shaft 76 are arranged so that the housing 75 will alternately be driven back and forth between predefined limits.

The twisting heads 51 through 54 grip the strand or spiral quad 45 frictionally in the direction of the circumference of the rollers contained therein. In a preferred embodiment all twisting heads revolve at the same speed of rotation. However, advantages can be obtained if the two twisting heads of the one or both accumulators are driven at different speeds of rotation. Similarly the speeds of one or both of the twisting heads of one or both of the accumulators may also be varied continuously or in discreet steps. By doing so it is possible to impart, to the spiral quad produced, a twist whose length of lay varies continuously as a function of the length of the spiral quad produced. When operating with a constant speed for all twisting heads, the back and forth motion of the housing 75 which continuously moves will result in varying speeds of the strand passing through the twisting heads thereby varying the amount of twisting imparted by each head. This in turn results in a different direction of twist being formed depending on which direction the housing 75 is moving. For a more detailed discussion of how variations in twist are obtained from twisting devices of this type, i.e. those in which variable length accumulators are used, see U.S. Pat. Nos. 3,169,360, 3,363,550 and 3,481,127.

A particularly advantageous twisting head for use in the twisting device of FIG. 1 is illustrated by FIGS. 2 and 3. The twisting head, designated generally as l, and which will be called a roller twister comprises essentially the two pairs of rollers 2 and 3 and 4 and 5. The two rollers of each pair are arranged on parallel axis and disposed with their running surfaces opposite each other. The rollers 2 and 4 are supported by an upper roll carrier 7 and the lower rolls 3 and 5 by a lower roll carrier 8. The roll carriers 7 and 8 are attached at one end to a left hand frame 9 and at the other a right hand frame 10. The entire twisting head is rotatably supported in conventional fashion about the axis of rotation 11. Although two pairs of rollers are shown herein, a single pair may be used as may a plurality of pairs greater than two. To adjust the spacing of the upper and lower rollers so that they may handle different sizes of strand 51, spindles 12 and 13 which are provided with a left handed thread at one end and a right handed thread at the other end are provided in frames 8 and 9. The upper and lower frames 7., 8 are guided by respective threaded sleeves l4 engaging the threaded portion of the spindles 12 and 13. A set screw 15 is provided to hold the spindles in place once the desired setting has been made.

The construction of each of the rollers 2, 3, 4, 5 is illustrated in FIG. 3 which is a plan view of the assembly of FIG. 2. In FIG. 3, the roller 4 is shown in a cut-away cross section. Essentially, it is made up of two roll halves l8 and 19 which are of symmetrical design and bolted together by bolts 20. The two halves are pressed against the outer race of a ball bearing which is axially secured to a sleeve 22 by means of a snap ring 23. The roller shaft 24 is led through the sleeve 22 and holds the roller between the upper roll carriers 7. The two halves of the roll 18 and 19 contain a grooved portion around their circumference. Into this groove 28 is fitted a friction winding 27 which is a rubber elastic material. The friction winding 29 is of a U-shaped cross section with its legs 30 and 31 abutting the inner surface of the groove 28. The bottom or base 29 of the U forms the running surface which grips the strand of FIG. 1. The hollow space 34 results in the ability flex and thus to firmly grip the strand 45 preventing any motion which would cause it to slip out from between the rollers but still permitting ease of pulling through the rollers. Ideally the friction lining 27 will be a closed ring which can be inserted into one of the sides l8, 19 prior to assembly. In addition the bottom of the groove should be painted with an adhesive prior to assembly so that the legs 30 and 31 will be firmly bonded to the bottom of the groove 28.

Particularly useful as a friction lining is a material having a basis of polyurethane such as that marketed by the firm Bayer-Leverkusen under the tradename Vulkollan.

Thus an improved SZ twisting device in which the strand being twisted is gripped and held in a stretched manner between the twisting heads of a breathing accumulator has been shown. Although a specific embodiment has been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit of the invention which is intended to be limited solely by the appended claims.

What is claimed is:

1. An SZ twisting device for twisting the stranding elements of a cable so as to form a stranded unit which has a twist direction which changes from section to section comprising:

a. an unwinding device for the stranding elements;

b. a drawing and take up device;

0. between said unwinding device and said drawing and take up device, an accumulator which has a storage content which may be increased and decreased comprising:

1. a first stationary rotating twisting head;

2. a second rotating twisting head movable with respect to said first twisting head in the direction of the twisting axis;

3. means for moving said second twisting head back and forth with respect to said first twisting head; and

4. each of said first and second twisting heads having rollers therein, and each of said first and second twisting heads gripping the stranding elements which are being combined into a stranded unit frictionally in the direction of the circumference of the rollers within said twisting heads so as to permit ease of pulling through of the stranded unit and holding the stranded unit in a stretched condition between the twisting heads.

2. The invention according to claim I and further including a second accumulator in tandem with said first accumulator said second accumulator having a third movable twisting head and a fourth stationary twisting head and wherein said means to move said second twisting head comprises a frame in which said second and third twisting heads are mounted and and means to move said frame back and forth in the direction of the strand.

3. The invention according to claim 2 wherein the speeds of rotation of at least one of said first and third twisting heads is different than that of said second and fourth twisting heads.

4. The invention according to claim 2 wherein the speed of rotation of at least one of said first and third twisting heads is varied with respect to the speed of said second and fourth twisting heads.

5. The invention according to claim 4, wherein each of said first and second twisting heads comprise:

a. at least one pair of rollers;

b. means supporting said rollers on parallel axes disposed opposite each other such that a strand may be gripped between said rollers and wherein each roller includes;

c. a groove running about the circumference of the roller over the major portion of the roller running surface width; and

d. a friction lining made of an elastic material embedded in said groove and bonded to the bottom thereof in a manner such that a hollow space is formed between the bottom of the groove and the portion of said lining forming the roller running surface.

6. The invention according to claim 5, wherein said friction lining has a U shape with the legs of the U bonded to the bottom of said groove and with the base of the U forming the running surface. 

1. An SZ twisting device for twisting the stranding elements of a cable so as to form a stranded unit which has a twist direction which changes from section to section comprising: a. an unwinding device for the stranding elements; b. a drawing and take up device; c. between said unwinding device and said drawing and take up device, an accumulator which has a storage content which may be increased and decreased comprising:
 1. a first stationary rotating twisting head;
 2. a second rotating twisting head movable with respect to said first twisting head in the direction of the twisting axis;
 3. means for moving said second twisting head back and forth with respect to said first twisting head; and
 4. each of said first and second twisting heads having rollers therein, and each of said first and second twisting heads gripping the stranding elements which are being combined into a stranded unit frictionally in the direction of the circumference of the rollers within said twisting heads so as to permit ease of pulling through of the stranded unit and holding the stranded unit in a stretched condition between the twisting heads.
 2. The invention according to claim 1 and further including a second accumulator in tandem with said first accumulator said second accumulator having a third movable twisting head and a fourth stationary twisting head and wherein said means to move said second twisting head comprises a frame in which said second and third twisting heads are mounted and and means to move said frame back and forth in the direction of the strand.
 2. a second rotating twisting head movable with respect to said first twisting head in the direction of the twisting axis;
 3. means for moving said second twisting head back and forth with respect to said first twisting head; and
 3. The invention according to claim 2 wherein the speeds of rotation of at least one of said first and third twisting heads is different than that of said second and fourth twisting heads.
 4. The invention according to claim 2 wherein the speed of rotation of at least one of said first and third twisting heads is varied with respect to the speed of said second and fourth twisting heads.
 4. each of said first and second twisting heads having rollers therein, and each of said first and second twisting heads gripping the stranding elements which are being combined into a stranded unit frictionally in the direction of the circumference of the rollers within said twisting heads so as to permit ease of pulling through of the stranded unit and holding the stranded unit in a stretched condition between the twisting heads.
 5. The invention according to claim 4, wherein each of said first and second twisting heads comprise: a. at least one pair of rollers; b. means supporting said rollers on parallel axes disposed opposite each other such that a strand may be gripped between said rollers and wherein each roller includes; c. a groove running about the circumference of the roller over the major portion of the roller running surface width; and d. a friction lining made of an elastic material embedded in said groove and bonded to the bottom thereof in a manner such that a hollow space is formed between the bottom of the groove and the portion of said lining forming the roller running surface.
 6. The invention according to claim 5, wherein said friction lining has a U shape with the legs of the U bonded to the bottom of said groove and with the base of the U forming the running surface. 